For privacy reasons some people don't want their Facebook profiles to be shown in search engines ( like  Google or Yahoo) because when someone searches for your name on search engines they can find your Facebook account.
If you want to  hide your Facebook profile from search engines just follow these steps :

1. Log in to your facebook account.

2. Go to Privacy sitting.

3. Scroll down to Ads, Apps and websites and click Edit sitting ( like in the picture ).

          
4. Scroll down to Public search and click Edit sitting ( like in the picture ).


 5. Now just uncheck Enable public search ( like in the picture ).